opening database from assets android studio

I know this question is very common and many people have already asked it. but even after doing alot of search i could not make it work. The idea is same, I have created a sqlite database with sqlite browser and added into my project assets directory in android studio.

Here is my class that I wrote and I check DB_PATH and DB_NAME etc, and all possible things but it is not working and throwing this error

open failed: ENOENT (No such file or directory)

code

public class DataBaseHelper extends SQLiteOpenHelper {

@Override
public void onCreate(SQLiteDatabase db) {

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion,
                      int newVersion) {

}

public DataBaseHelper(Context context){
    super(context, DB_NAME, null, 1);
    this.ctx = context;
    if(android.os.Build.VERSION.SDK_INT >= 17){
        DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
    }
    else
    {
        DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
    }
    accessDatabase();
}

private void accessDatabase(){
    if(checkDatabase()) {
        Log.d(TAG, "CHECK DB existence" + checkDatabase());
    } else {
        copyDataBase();
        Log.d(TAG, "DATABase Copied");
    }
}

private boolean checkDatabase() {
    SQLiteDatabase checkDB = null;
    try {
        String dbPath = DB_PATH+DB_NAME;
        File file = new File(dbPath);
        if (file.exists() && !file.isDirectory())
            checkDB = SQLiteDatabase.openDatabase(dbPath, null,SQLiteDatabase.OPEN_READWRITE);
    }catch (SQLiteException exception){
        exception.printStackTrace();
    }
    return checkDB != null ? true : false;
}

private void copyDataBase() {
    try {
        InputStream myInput = ctx.getAssets().open(DB_NAME);
        Log.d(TAG, "DB_PATH- "+DB_PATH+DB_NAME);
        String outFileName = DB_PATH + DB_NAME;
        OutputStream myOutput = new FileOutputStream(outFileName);
        byte[] buffer = new byte[1024];
        int length;
        while ((length = myInput.read(buffer)) > 0) {
            myOutput.write(buffer, 0, length);
        }
        myOutput.flush();
        myOutput.close();
        myInput.close();
    }catch (IOException exception){
        exception.printStackTrace();
    }
}

private static String DB_PATH = null;
private static String DB_NAME = "database.db";
private Context ctx;

private static String TAG = "DataBaseHandler";

}

PATH(s) and NAME(s) are correct and I am running it on Android Lollipop